Method of electric welding



July 17, 1928.

' 1,677,206 E. PUGH METHOD OF ELECTRIG WELDING Filed April 17, 1926 'Patented July 17, 1928.

UNITED STATES y A 1,677,206 PATENT OFFICE.

I EMERSON PUGH,OF CHICAGO, ILLINOIS,4 ASSIGNOR TO WESTERN .ELECTRIC COMPANY,

INCORPORATED, Ol?l NEW YORK, N. Y., A CORPORATION OF N YORK.

KETHOD'O-F ELECTRIC WELDING.

Application led April 17, 1926. Serial No. 102,650.

This invention relates to methods of welding, and more particularly to methods of electrically welding metal parts.

It is sometimes desirable to electrically ,n weld metal parts Without destroying the smoothness an,d other .physical characteristics of the surfaces thereof. An'instance of this nature is encountered in certain types of electrical sound translating apparatus, 1n

audiophone and'having a lated diaphragm of duralumin to one sur ace of which an electrical conductor in the. form of aver thin strip of gold foil iselectrically welde l It is essential for the proper functioning of the transmit-ter that the surfaces of the welded lparts be -free from pin holes or pits which might be produced during the Welding operation. A v

Objects of the invention are to provide a simple method of welding parts, particularly thin metal parts, without deleteriously deforming the surface thereof.

In order to attain these objects, in accordance with one embodiment of the invention, the metallic electrodes connected with the weldinglcircuit are each covered with a thin layer or film of graphite which keeps the metallic surfaces of the electrodes and the parts being weldedseparated and at the same time retains the advantages to` be gained by using metallic electrodes.

It is believed thatacomplete understanding of the invention maybe had from the following description taken in conjunction with the accompanying drawing, in which:

Fig. 1 shows diagrammatically the application of the method to the welding of a strip of gold leaf to a gold plated duralulmin diaphragm; i

Fig. 2 isa plan view ofthe diaphragm with the strip of gold leaf welded thereto, and

Fig. 3'is a cross-sectionalview of an, 4.a

phragm connected inthe primary circuit of an audiophone set ofthe type shown in the copending application of G. R. Lum, Serial No. 721,509,11ed Junev 21, 1924.

In the construction of audiophone transvmitters it is desirable to make the trans- 'mitter as small and compact as possible. The diaphra m 1 is, therefore, used as one transmitter e ectrode and consists of a sheet of duralumin about .01 inches in thickness such as a telephonie transmitter used inlanv audiophone transmitter showingA the dia-` and 1.125 inches in diameter. In .order to .obtain a good contact between the diaphragm 1 and the granulated carbon 3 when theidiaphragm is in vibration, the diaphragm is gold plated. When the, diaphragm is used in this way as one ofthe transmitter electrodes it is necessary to attach a. conductor to the diaphragm in such a manner that it will not interfere with or dampen the vibrations of the diaphragm. For this purpose al strip of gold foil 2 having a thickness of .005 inch is employed. The strip of gold foil 2 is welded to the diaphragm 1 as indicated at 4.

In the process of welding the gold foil to the diaphragm, it appears that in spite of the fact that the lower electrode 5 is made much larger than the area t0 be welded it does not sufficiently reduce the current density to always prevent the 'adhesion of the gold plate to the electrode. The adhesion may l'produce pits or pin-'holes in the gold plate which would cause the diaphragm to produce' a so-called frying sound in the receiver associated. therewith.

The 'application of a non-metallic substance, as for instance a thin layer of graphite, such as may be -made by rubbing 'a soft pencil over the surface of the electrode, produces a film of material which is a conductor of electricity, but which will not alloy with or adhere to the gold plate sufciently to cause it to tear loose when removed from the electrode and thus permits the weld to be made without any damage to the surface of the gold plated diaphragm. 4

This methodl 'permits the use of a large metallic electrode 5 which serves to conduct heat away Afrom the lower side ofthe diaphragm and thereby prevents excessive heating at the point of contact. y

The application of the method is as follows: The electrodes 5 and 6 are coated with a thin film of graphite. The diaphragm 1 and the 'gold leaf strip 2 are then placed on 100 the electrode 5 and the electrode is brought in contact with the gold leaf strip. A current "of about 150 amperes is caused to flow through the com aratively small area of the electrode u6 whicli causes a concentration of 105 the current where this electrode contacts and produces a weld between the gold plated diaphragm and the gold leaf.

' Fig. 3 illustrates the diaphragm operatively mounted in the primary circuit of an H0 audiphone set vof the type disclosed in the copending application referred to above. The vibration of the diaphragm causes a variation-of the resistance of the granulated carbon and an alternating current is thereby produced in the secondary 7 of the transformer 8 as is Well understood in the art. The secondary of the transformer is connected to the output circuit of the set.

It Will be understood that the application of the invention herein described and'illusrated is merely by Way of example and that scope of the invention.

What is claimed is: 1. The method lof Welding thin metals which consists in covering almetallic elec- A trode With a thin layer of a non-metallic conducting substance to prevent adhesion to the Work, positioning the metals and the electrode in electrically conducting relation separated by the layer of the non-metallic conducting substance and passing a current through the electrode and the metals.

2. The method of Welding goldvfoil, which consists of applying a thin layer of graphite to a metallic electrode, positioning the foil and the elect-rode in electrically conducting relation separated by the layer of graphite, and passing a current through the electrode and the foil.

In witness whereof, I hereunto subscribe my name this 31 day of March A. D., 1926.

EMERSON PUGH. 

